Construction machines, such as track-type tractors, hydraulic excavators, and hydraulic mining shovels usually have a pair of track assemblies as ground engaging members. Such track assemblies may include a pair of tracks, each track having a number of track shoes arranged around a fixed track frame, on either side of a machine for supporting the weight of the machine and payload, and providing traction in a variety of conditions. For a given drive force, the traction of the machine is limited by a ground contact surface area of the tracks and a ground pressure acting between the tracks and the ground surface. In applications such as dozing, drilling, and pile driving, when a tool fixed to a front end of the machine is applied to the ground surface, a rear end of the machine experiences more ground pressure in comparison to the front end causing imbalanced loading on the tracks. In applications such as ripping, towed scraping and levelling, when the tool is applied to the ground surface behind the machine, the rear end of the machine is unevenly loaded compared to the front end and therefore, experiences a lower ground pressure. Such uneven loading of the track assemblies can lead to premature wear and reduced traction.
Further, in order to operate the tool, the weight of the machine may be used to apply a pressure on the tool. The pressure on the tool may be dependent on the weight of the machine and the ground pressure on the tracks. In order to increase the pressure, the traction may be increased by increasing the payload on the machine. However, increasing the payload on the machine just to increase the traction is not always a feasible solution. Often, the pressure on the tool is also increased by adding weight to the tool or applying extra force to the tool through hydraulic cylinders or another similar mechanism. Increasing the pressure on the tool in this manner creates uneven loading in the track assembly, reduces the ground pressure under the tracks adjacent to work tool, and in turn limits the available traction.
Chinese Patent No. 103158797A (hereinafter the '797 patent), shows an underwater unmanned remote-control heavy-load work vehicle. The vehicle comprises a frame, a first walking caterpillar band, a second walking caterpillar band, an electronic cabin, a hydraulic valve cabin, a hydraulic pump station cabin, a right swing arm auxiliary caterpillar band and a right swing arm auxiliary caterpillar band. Two ends of a left swing arm auxiliary caterpillar band driving oil cylinder and a right swing arm auxiliary caterpillar band driving oil cylinder are respectively hinged on the frame and a left swing arm auxiliary caterpillar band support frame of the left swing arm auxiliary caterpillar band and a right swing arm auxiliary caterpillar band support frame of the right swing arm auxiliary caterpillar band on corresponding sides. The hydraulic oil cylinders are used to drive the triangular auxiliary caterpillar bands to swing, moving ranges are big, underwater work is easy to carry out, a structure is simple, weight is light, installation and maintenance are easy and convenient, and cost is saved. The oil cylinders are easy to lock, good in rigidity, and capable of carrying out underwater heavy-load work. By adopting a hydraulic oil cylinder swing arm driving system, the trafficability and the obstacle climbing ability of the underwater unmanned remote-control heavy-load work vehicle under complex environments are greatly improved, and the adaptability of the underwater unmanned remote-control heavy-load work vehicle in the seabed underwater complex environments is greatly enhanced. The underwater unmanned remote-control heavy-load work vehicle disclosed by the '797 patent does not disclose a track assembly having a pivotable portion.